PENINGKATAN KETAHANAN AUS PERMUKAAN BAJA KONSTRUKSI ST-42 MELALUI SUBSTITUSI ENERGIZER CANGKANG KEPITING (CACO3) PADA PROSES PACK CARBURIZING DAN PENEMPERAN

Abstract

Low-carbon steel ST-42 is a material widely applied in general mechanical construction, yet it exhibits technical limitations regarding its surface hardness. This study aims to investigate the effect of varying tempering temperatures (200°C, 300°C, 400°C, 500°C, and 600°C) on the hardness value of St-42 steel following a surface hardening process using the pack carburizing method. As an eco-friendly biomaterial innovation, this research substitutes the use of synthetic Barium Carbonate (BaCO₃) with crab shell waste which is rich in Calcium Carbonate (CaCO₃) acting as a catalyst (energizer), combined with walnut shell carbon powder. A quantitative laboratory experiment was conducted utilizing 15 plate test specimens, where mechanical properties were measured using the Rockwell method (HRC).  The results demonstrated that crab shells operate highly effectively in accelerating carbon diffusion; the average initial hardness of the steel increased drastically from 112.6 HRC to approximately 138.5 HRC post-carburizing and rapid quenching using SAE 20-50 oil. The tempering stage revealed an inversely proportional empirical correlation between temperature and material hardness. Low-temperature tempering (200°C–300°C) successfully maintained hardness retention at around 135 HRC through epsilon carbide precipitation, whereas high-temperature tempering (500°C–600°C) drastically reduced hardness to 125.325 HRC due to cementite spheroidization and carbide agglomeration. In conclusion, crab shell waste serves as a highly reliable alternative energizer, and tempering temperature parameters can be precisely engineered to achieve an optimal equilibrium between surface wear resistance and material toughness for industrial machinery components.

Keywords: ST-42 Steel, Pack Carburizing, Crab Shell, Tempering, Rockwell Hardness.